The U.S. airline industry will carry fewer passengers on fewer flights, and domestic air traffic will decline by as much as 2 percent in 2013, according to a report released Tuesday by Evergreen, Colo.-based aviation consulting firm Boyd Group International.

The group credits the decline to the elimination of 50-seat regional jets by most major carriers over the next few years, with U.S. carriers on track to retire nearly 1,000 of these smaller jets by 2017. The report also notes growth rates in subsequent years will be slower than previously expected, with airports handling 50 million fewer passengers in 2017 than FAA is currently forecasting.

"Airline traffic can no longer be forecast simply with mathematical formulas based on metrics such as GDP, inflation, buying power and the like," said Michael Boyd, chairman of the Boyd Group International. "There are only 10 major full-schedule airline systems left, and each has its own subjective strategy in regard to where and if it adds capacity."

Boyd said the retirement of regional jets would be “revenue positive,” particularly at smaller airports where some of these jets are operating in excess of 80 percent capacity.

The firm also predicts carriers will continue to have strong demand for next-generation fuel efficient aircraft such as the Boeing 737 MAX and Airbus A320neo. More